The main goal of this project is to investigate whether dietary isoflavones such as genistein can inhibit prostate cancer growth through activation of tumor suppressor microRNAs (miRNAs) using both in vitro and in vivo models. Prostate cancer is the most common male malignancy and the second leading cause of cancer death among men in the United States. The rationale for this project is that recent studies have shown significant effects of diet on modulation of miRNAs using both in vitro and in vivo models. Based on our preliminary data and published literature, we hypothesize that genistein can activate a set of tumor suppressor miRNAs thereby inhibiting prostate cancer progression through two different pathways. First, genistein induced tumor suppressor miRNAs can repress oncogene expression by binding to the 3' untranslated region of mRNA (3'UTR). Second genistein induced tumor suppressor miRNAs can activate the transcription of tumor suppressor genes by binding to the 5' upstream region of the gene or activate translation by binding to the 5' untranslated region of mRNA (5'UTR). This project is novel and timely because the roles of genistein mediated activation of tumor suppressor miRNAs in the regulation of prostate cancer progression have not been investigated. We also hypothesize that the molecular mechanism of genistein's mediated activation of tumor suppressor miRNAs are through epigenetic pathways. These hypotheses will be tested by pursuing the following three specific aims. Specific Aim # 1. To test the hypothesis that genistein mediated activation of tumor suppressor microRNAs are involved in the regulation of prostate cancer. Specific Aim # 2: To test the hypothesis that DNA methylation and histone modifications are the key mechanisms of genistein mediated activation of microRNAs in prostate cancer. Specific Aim # 3: To test the hypothesis that genistein can suppress prostate cancer growth in a nude mouse model through activation of microRNAs. Impact: The project will provide a novel paradigm with high impact in the field of management of prostate cancer since dietary mediated activation of tumor suppressor miRNAs and their roles in the inhibition of prostate cancer progression have never been investigated. Successful accomplishment of these experiments will provide novel strategies for the treatment of prostate cancer.